The Panasonic HDC-SD90 (and HDC-TM90) has several good features that interest me for shooting nature. It has a 26x zoom lens with minimal flaring and chromatic aberration. It has manual control, albeit with rather clumsy menu driven control, and it produces quite a good quality HD video picture for a consumer camcorder.
But there were a few things I could improve, so I decided to make some modifications to the camcorder as a fun project. This is what my modification adds:
- Lens hood with the capability of attaching 67mm filters without vignetting.
- Power supply for the microphone which is switched on automatically when the camera is switched on
- 2 XLR sockets for attaching external microphones. Each channel can be individually switched between the internal mic and the external input.
- Manual gain controls for each audio channel.
- High capacity battery with a running time of at least 4.5 hours.
- Charging circuit for the built-in battery.
- Four LED battery condition meter.
- Regulator to run the camera and charge the battery from 12VDC.
- Removable LCD hood.
- Quick-release tripod plate.
This article does not give step by step instructions for reproducing the project, but should offer some ideas and information for anyone contemplating a similar project. This is not something you would want to do to save money on a more professional camcorder, but rather a project done for its own sake. There was a lot of time involved.
This is made from two lengths of 12mm square channel aluminium with two 3mm plates on top. The electronics case and lens hood are screwed to this, and a single screw into the SD90’s tripod mount is all that’s required to hold the SD90 in place between them. An empty area is left in the centre to allow access to the SD card. There are also two brackets made from U-channel to facilitate locking with the quick-release tripod plate.
The lens hood and the electronics box are each made from an ABS project box 125L x 85W x 55H mm. A large rectangular hole was cut in the top cover to form the front of the hood and I cut an oval hole in the base to allow the front of the camcorder to poke into the hood. The edge of this hole has a narrow strip of felt glued to it to make a light seal and to protect the camcorder from scratches as it is fitted.
A 0.5mm deep round groove was cut around the camcorder opening to accommodate the filter thread, which is made from an old 67mm UV filter with the glass removed. I drilled a series of 1mm holes around the base of the filter and glued it in place with fibreglass resin and a few glass fibres through the holes to add strength. I also moulded a fibreglass strut on the back of the lens hood for attaching the handle. A few holes through the box for the resin to fill helped to add strength to the strut.
Handle & Microphone
The handle is another length of 12mm square box section aluminium and is screwed into the fibreglass struts with 2 very long screws. I used a few rivet-nuts to allow an ABS mic holder to be screwed to the handle and also allow for possible future accessories to be attached. The internal microphone is simply a small omni-directional condenser mic insert embedded in a piece of foam plastic. There is another piece of foam in front of it to act as a windscreen.
This is the area most of the design and construction time was spent. The box contains a 7.2V battery made from six AA 2400mAh NiMH cells, the XLR and DC sockets and the PCB. I used a hot-air gun to mould a depression allowing thumb access to the record start-stop switch on the camcorder, and also made a fibreglass strut for attaching the rear end of the handle. A wedge-shaped piece of ABS was glued to the bottom so the box would mount vertically on the base plate. The final step for the box and lens hood was to paint them with plastic primer and matt black acrylic lacquer (car paint).
The NiMH cells were mounted in the back of the box and an isolation switch was mounted on the top of the box for safety. The PCB was attached to the lid of the box using threaded spacers which allowed me to mount components on both sides of the PCB.
The electronic circuit consists of a 5V switching regulator, charging circuit controlled by an Atmel ATTINY26 microcontroller and audio switching and level controls. I used the body of an IDC connector with its pins removed to act as a spacer for the four 3mm LEDs.
Download AVR Assembler Firmware: sd90mod-firmware.zip
Size:5.6 KB – 395 downloads
Download Schematic and PCB Layout: sd90mod.zip
Size:266.0 KB – 379 downloads
The camcorder requires 5 volts to operate via it’s DC input and a LM2575 switching regulator supplies this from the 7.2V battery or external 12V supply. A current sense wire runs to the camcorder power plug negative terminal and is fed to a LM358 op-amp. This is used to amplify the very small voltage drop on the negative wire and is fed to the microcontroller as the camcorder on-detect signal.
The battery is controlled by a MOSFET that serves 2 purposes. When there is no external 12V, the MOSFET is switched on to connect the battery to the input of the 5V regulator. When the external 12V is present and charging mode is active, the MOSFET is driven by a PWM output from the microcontroller to control charge current.
This is made from 3mm aluminium and has a spring loaded catch at the end to lock the camcorder base plate in place.
The LCD hood is moulded from fibreglass. I completely wrapped the camcorder in multiple layers of 5 day masking tape, painted the LCD area with release wax and moulded the fibreglass directly around the LCD display. I then ground the surfaces smooth, painted it and glued a piece of felt to the inside to protect the camcorder as it is fitted and removed.